Eugène Papirer

XPS study of the halogenation of carbon black—Part 2. Chlorination

Abstract Three furnace carbon blacks, a thermal black, and an electrically conductive sample were submitted as received to chlorination, at 450 °C, with a mix of chlorine and carbon tetrachloride vapors. The treated samples were examined using chemical and spectroscopic (XPS) methods. The interpretation of the XPS spectra is facilitated by comparison with spectra of reference materials. XPS detects various types of carbon-chloride bonds formed essentially by addition or hydrogen substitution processes. The amount of fixed chlorine is dependent on the origin of the blacks, and there is no direct relationship between specific surface area and chlorine uptake. It is shown that chlorination is not limited to the external surface, nor is it to a sub-superficial layer. In fact, it proceeds inside the carbon black particles to a depth depending on their origin.

Contribution to the study of basic surface groups on carbons

Abstract An attempt is made to increase and to understand the formation of basic groups on the surface of carbon black. The total number of basic groups is increased by an oxidation/heat treatment process, but not the surface coverage. The formation of pyrone-type structures occurs by air reexposure of the heat treated blacks in combination with heat resistant carbonyl groups.

Gas-solid chromatography : a quick method of estimating surface free energy variations induced by the treatment of short glass fibers

Retention volumes for a series of n-alkanes and “polar” adsorbates having sizes consistent with the highest-sensitivity range of a katharometer detector were measured using short glass fibers as the column packing. Retention data were shown to be dependent on the nature of the surface treatment of the solid substrate. Silane-treated and titanate-treated glass fibers showed opposite behaviors with respect to the untreated solid, especially as far as specific interaction are concerned; silane treatment was found to decrease the ability of the glass fibers to interact with good electron-donor probes while a corresponding increase was evidenced in the case of titanate treatment. A parallel was drawn between these observations and the qualitative appreciation of the adhesion between fibers in composite materials made of the untreated or treated glass fibers and a phenolic resin.

Surface properties of a calcium carbonate filler treated with stearic acid

Abstract The fixation of stearic acid on a CaCO3 filler and the induced changes in surface properties have been studied. The chemisorption isotherm of stearic acid was established using a tracer (tritium) method. Nitrogen adsorption, contact angle measurements and inverse gas chromatography at infinite dilution revealed a drastic decrease in surface energy, as a function of the degree of surface coverage by stearic acid. The totally covered CaCO3 exhibits a surface energy close to that of pure stearic acid, with no surface polarity.

Surface groups on nitric acid oxidized carbon black samples determined by chemical and thermodesorption analyses

Abstract Spheron 6 was oxidized with 1 1 nitric acid and the treated samples were submitted to elemental analysis and oxygenated surface group determination. The active surface area (ASA) of the samples was measured. Analysis was made of the gases (CO, CO2) evolved when the oxidized samples were heat treated up to 950°C. It is shown that the amount of oxygen which chemisorbs at 100°C on the preheated (800°C) carbon blacks corresponds to the amount of base-like groups (pyrone) which are formed after re-exposure to air.

Characterization and modification of fillers for paints and coatings

This paper highlights the possibility of inverse gas chromatography for the surface characterization of common fillers (CaCO3, talc, SiO2,⋯) for paints and coatings. Divided solids are described, on the one hand, by the dispersive component of their surface energy and, on the other, by a specific parameter indicating their acid-base interaction potential. The role of the surface morphology at a molecular level is also examined. It is demonstrated that steric effects play an important role in the adsorption of probes on lamellar solids like talc. The consequences of surface treatments as well as examples of practical applications are also reported.

Contribution to the study of the surface groups on carbons—II: Spectroscopic methods

Abstract Electron spectroscopy was applied to the study of a colour black (Carbolac 1) and of graphitic oxide, modified by esterification of the acidic surface groups. The deconvolution of the Ols spectra indicates that in the case of carbon black irreversible transformations of the surface structure occur. On the contrary, for the methylated graphite oxide, a subsequent hydrolysis of the ester groups restores the original structure. IR Spectroscopy (transmission and internal reflection spectroscopies) confirms this observation: the irreversible transformation intervenes during the hydrolysis step of the methylated black. Use of a tracer technique gives direct support to the hypothesis of an enol structure which appears to become partially blocked. Possibly, the labile hydrogen involved in the keto-enol equilibrium is substituted by an alkyl group. The differences in behaviour of the surface groups of carbon black and graphite oxide can be explained on the basis of their location on solid supports having different electronic properties.

The surface energy of silicas, grafted with alkyl chains of increasing lengths, as measured by contact angle techniques

Silica, modified by esterification with linear alcohols having between 1 and 20 carbon atoms, is compacted into smooth discs. Their surface polarity, measured by contact angle techniques, decreases with increasing surface coverage and chain length of the grafts. For the longer chains, the surface energy of the grafted silicas reaches a value close to the one of poly(ethylene). The spreading pressures of water on the modified silicas were measured either by contact angle or vapor adsorption techniques.

Chemical nature and water/oil emulsifying properties of asphaltenes

Abstract Asphaltenes which differ in their abilities to form water/oil emulsions were analysed by acidimetry, infrared and nuclear magnetic resonance spectroscopies. Asphaltenes which easily form such emulsions are loosely packed molecules and exhibit a marked acid/base imbalance.

Surface characteristics of commercial carbon fibres determined by inverse gas chromatography

Abstract The surface characteristics of carbonized and stabilized carbon fibres have been studied using inverse gas chromatography. First, the dispersive component of the surface energy of both types of fibres was determined. Secondly, using polar probes of known properties, acid-base surface characteristics of the fibres were obtained. It has been shown that the carbonized fibres exhibit an electron donating (base) character, whereas stabilized fibres are more amphoteric.